A wireless biofluid pH sensor based on a biomass-derived carbon/polyaniline hydrogel

Flexible sweat pH electrodes require sensing layers that combine a proton response with mechanical deformability. Here, we prepared a composite hydrogel sensing layer (CPN-AB + PVA) by in situ oxidative polymerization, combining boronic acid-functionalized polyaniline, corn-stalk-derived porous carbon and a polyvinyl alcohol (PVA) network. Interactions between the boronic acid-functionalized polymer and PVA connect the proton-responsive component with a stretchable network. The hydrogel exhibited an elongation at break of 285%. The resulting electrode achieved a sensitivity of 85.62 ± 0.79 mV pH − 1 in buffers from pH 2.00 to 8.00 and retained a linear potentiometric response under bending. Coupling the electrode with a Bluetooth readout module enabled continuous sweat pH recording during exercise. The composite sensing layer brings together mechanical deformability and high potentiometric sensitivity for flexible sweat pH measurement.